The invention relates to a valve flap for forming a valve, in particular for a casting machine, to a valve, and to a valve system, in particular for installation in a casting machine for casting a flowable mass, and to a casting machine for casting a flowable mass, in particular a liquid mass containing suspended solid particles, such as chocolate. The invention further relates to a casting machine, to a method for forming a valve system, to a method for adapting a casting machine valve system, to an assembly kit for forming a casting machine valve system, and to a method for converting a casting machine.
Known casting machines for the casting of chocolate contain, for example, a mass tank for receiving flowable mass, at least one valve, which is fluidically connected to the interior of the mass tank, wherein the valve, given the presence of a pressure gradient along its valve passage direction, is in an open state and, given the non-presence of this pressure gradient along its valve passage direction, is in a closed state; as well as a pressure generating means for generating a pressure gradient along the valve passage direction of the valve.
In this context, flowable masses are masses which either flow by themselves due to gravitational force and/or which are conveyable by means of a pump.
The pressure can be generated, for instance, by means of a piston device, with which portioned volumes of the mass are pulled or pushed into metering chambers and are pressed or poured out of these same through nozzles onto a support or into hollow molds.
In some particular models of casting machines of this type, the valve function is coupled with the piston function. For this, the piston is configured, for example, as a substantially cylindrical reciprocating and/or rotary piston, wherein, through a succession of reciprocating and/or rotary motions of the respective piston in a first direction and an opposite second direction, a full casting cycle (induction and expulsion) can be performed.
In most applications in which chocolate mass is cast, the casting takes place at such high temperatures that the chocolate mass as a whole is present in a really highly fluid state and an afterflow at the nozzles can ensue.
It has therefore proved advantageous to use nozzle flaps which are articulately connected to the valve body and are subjected to an elastic pretensioning which forces the valve flap against the valve opening and seals this off.
Valves having elastic valve flaps can also be used. For instance, valves whose valve flaps are shaped by the regions between slot-like openings in a valve body are known. As the slots are being cut, the valve structure can, however, be undefinedly damaged, whereby the working of the sealing surfaces can be impaired. The rims of the slots are inclined to crack under stress, whereby the working life, in the present case the number of possible closing cycles, is reduced.
Moreover, it has proved difficult in practice to furnish the valve flaps in a slotted valve body with a defined pretensioning.
Valves of this type therefore frequently fail to meet the requirements with regard to precise metering, particularly in the case of high clock frequencies and small metering quantities.